Posted by: Thixia | April 5, 2008

Urinary Dysfunction and MS 2 of 6

Types of bladder dysfunction in MS

MS-related lesions (areas of inflammation, demyelination, scarring and/or neuronal damage) in the brain or spinal cord can disrupt this normal process by interfering with the transmission of signals between the brain and urinary system.  Three primary types of bladder dysfunction can result: 

Storage dysfunction 

Failure to store urine is caused, in part, by an overactive detrusor muscle that begins to contract as soon as a small amount of urine has collected in the bladder.  These contractions repeatedly signal the need to void, even though the bladder has not reached normal capacity.  Because of demyelination, the spinal cord is unable to forward the signals from the bladder all the way to the brain.  Without the involvement of the brain, the process of urination becomes less controlled.  The urge to urinate becomes a reflex response to the frequent, repeated spinal cord signals.  This type of storage dysfunction can result in the following symptoms:

  • Urgency – the inability to delay urination once the urge to void has been felt
  • Frequency – the need to urinate in spite of having voided very recently
  • Nocturia – the need to urinate during the night
  • Incontinence – the inability to control the time and place of urination

Emptying dysfunction 

Demyelination in the area of the spinal cord that signals the voiding reflex can also result in a failure to empty the bladder.  Although the bladder fills with urine, the spinal cord is unable to send the appropriate message to the brain (to signal the need to void) or to the external sphincter (to signal the need to relax).  In the absence of voluntary control, the bladder continues to fill and expand.  The eventual result is an enlarged, flaccid (overly relaxed) bladder, accompanied by the following symptoms:

  • Urgency –
  • the inability to delay urination once the urge to void has been felt
  • Dribbling – uncontrolled leakage of urineHesitancy – delay in ability to initiate urination even though the need to void is felt
  • Incontinence – the inability to control the time and place of urination
  • Combined dysfunction Failure to store in combination with failure to empty (formally known as detrusor-external sphincter dyssynergia) results from a lack of coordination between muscle groups.

Instead of working in coordination with one another (with the detrusor contracting to expel urine while the external sphincter relaxes to release it), the detrusor and external sphincter contract simultaneously, trapping the urine in the bladder.  The resulting symptoms can include:

  • Urgency
  • Hesitancy
  • Dribbling
  • Incontinence 
  • Urinary tract infection 

In addition to these common types of bladder dysfunction, people with MS are at increased risk of urinary tract infections.  Although anyone can develop an infection in the urinary tract, they are more common in people who are unable to fully empty their bladder.  Urine that remains in the bladder over a prolonged period of time breeds excessive bacteria, eventually leading to infection.  Storage of urine also allows mineral deposits to settle and form stones that promote infection and irritate bladder tissues. 

The symptoms of a urinary tract infection can include:

  • Urgency
  • Frequency
  • A burning sensation
  • Abdominal and/or lower back pain
  • Elevated body temperature
  • Increased spasticity (a common symptom of MS caused by an abnormal increase in muscle tone that results in involuntary muscle stiffness and/or spasms)
  • Dark-coloured, foul-smelling urine

A person who has a urinary tract infection may also experience a pseudo-exacerbation.  The infection and accompanying elevation in body temperature may cause other MS symptoms to flare temporarily, mimicking a true exacerbation, even though there is no underlying disease activity.  Once the infection has been treated, these MS symptoms resolve and return to the person’s pre-infection baseline.  Thus health-care providers look for bladder symptoms or other evidence of infection when trying to determine if a person is having an exacerbation.  



Compliments of:

Multiple Sclerosis Society of Canada


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